This invention relates to fluorescent lamps and, more particularly, to fluorescent lamps which incorporate exteriorly coated luminescent material to provide additional desired longer wavelength visible radiations.
Discharge devices which utilize organic phosphor or luminescent material are known and are described in U.S. Pat. No. 2,177,701 dated Oct. 31, 1939 to Fonda. U.S. Pat. No. 4,001,628 dated Jan. 4, 1977 to Ryan discloses a fluorescent lamp wherein longer wavelength visible radiations are supplied by organic phosphor which is disposed in a predetermined pattern, such as a series of polka dots, on the exterior surface of the fluorescent lamp envelope. While the performance of such a lamp is excellent, unless it is utilized in a fixture with a diffusing shield, the red-appearing phosphor polka dots have been reported as aesthetically bothersome to some people.